This disclosure relates to releasable attachment devices of the type used to fasten, retain, or latch together components of an apparatus or a structure that are to be separated or released under controlled conditions. This disclosure further relates to releasable attachment devices that provide variable damping capabilities.
Hook and loop type separable fasteners are well known and are used to join two members detachably to each other. These types of fasteners generally have two components disposed on opposing member surfaces. One component typically includes a plurality of resilient hooks while the other component typically includes a plurality of loops. When the two components are pressed together they interlock to form a releasable engagement. The resulting joint created by the engagement is relatively resistant to shear and pull forces, and weak in peel strength forces. As such, peeling one component from the other component can be used to separate the components with a minimal applied force. As used herein, the term “shear” refers to an action or stress resulting from applied forces that causes or tends to cause two contiguous parts of a body to slide relatively to each other in a direction parallel to their plane of contact. The term “pull force” refers to an action or stress resulting from applied forces that causes or tends to cause two contiguous parts of a body to move relative to each other in a direction perpendicular to their plane of contact.
Magnetorheological (MR) elastomers are known as “smart” materials whose rheological properties are rapidly changed upon application of a magnetic field. MR elastomers are suspensions of micrometer- or nanometer-sized, magnetically polarizable particulates embedded in an elastomeric polymer or rubber. The stiffness of the MR elastomer structure is accomplished by changing the shear and compression/tension moduli by varying the strength of the applied magnetic field. The stronger the magnetic field, the stiffer the MR elastomer will be. The MR elastomer typically develops structure when exposed to a magnetic field in as little as a few milliseconds. Discontinuing the exposure of the MR elastomer to the magnetic field reverses the process and the MR elastomer returns to its lower modulus state. Because of the ability to vary the modulus or stiffness of the MR elastomer on demand, MR elastomers have found use as components in damping devices.